\documentclass[a4paper]{article}
\usepackage{booktabs}
\usepackage{bibentry}
%\usepackage[style=verbose]{biblatex}
\usepackage[total={170mm,277mm}, left=20mm, top=10mm]{geometry}
\thispagestyle{empty}
\renewcommand{\labelitemi}{--}
\usepackage{tabularx}
\usepackage{longtable}

\usepackage[backend=biber,maxnames=12]{biblatex}
\bibliography{../bibliography.bib}


\begin{document}

\begin{flushright}
  {{tday}}
\end{flushright}

\medskip

\begin{center}
  {\bf Declaration}
\end{center}

\bigskip

I hereby declare that the contribution to the following paper:

\smallskip

\noindent\fullcite{this-paper}

\smallskip

\noindent is correctly characterized in the table below{% if nb_of_levels == 0 %}.{% elif nb_of_levels == 1 %} ({{ level_symbols[0] }} denotes equal contributions).{% else %} ({% for lix in range(nb_of_levels) %}{% if lix == nb_of_levels - 1 %}{} and {{ level_symbols[lix] }}{} denote groups of equal contributions).{% elif lix == 0 %}{{ level_symbols[lix] }}{% else %}, {{ level_symbols[lix] }}{% endif %}{% endfor %}{% endif %}
\medskip



\begin{center}
\begin{longtable}{lc}
\toprule
\addlinespace[0.05cm]
Contributor & Description of main tasks \\
\addlinespace[0.05cm]
\midrule
\addlinespace[0.1cm]
{% for author in data['authors'] %}
{{ author['author'] }}{% if 'level' in author %}{{level_symbols[author['level']-1]}}{% endif %}
&
\begin{minipage} [t] {0.6\textwidth}
\begin{itemize}
\itemsep=0em
{% for citem in author['contributions'] %}
\item {{citem}}
{% endfor %}
\end{itemize}
\end{minipage} \\
{% if loop.index == loop.length %}
\addlinespace[0.25cm]
{% else %}
\addlinespace[0.5cm]
{% endif %}
{% endfor %}
\bottomrule
\end{longtable}
\end{center}

\vskip 0.8cm

\begin{tabularx}{\textwidth}{XXXX}
{% for author in data['authors'] %}
{{ author['author'] }}
{% if loop.index == loop.length %}
\\
{% elif loop.index % 4 == 0 %}
\\ \addlinespace[0.5cm]
{% else %}
&
{% endif %}
{% endfor %}
\end{tabularx}

\end{document}